Blown turbochargers, snapped timing chains, smoking engines – all these and more can result from delaying an oil change or using the wrong oil. Ask for the service history and take time to look through it. If a service is due negotiate on the price, but if the history’s missing, walk away

Dashboard lights are important. Check all the systems such as ABS and stability control. Make sure they all light up when you turn on the ignition and go out after a few seconds or when you start the engine. Check the handbook if you’re not sure you’ve seen them all

After starting the engine, listen carefully for the first few seconds – any knocks or rattles are bad signs. Grey exhaust smoke is a sign of a worn engine – check it after your test drive when the engine is hot

As well as checking the suspension by listening for rattles or clunks over rough roads, try stopping at different rates – gently and rapidly. The engine should never stall as the car stops and the revs shouldn’t drop very low and then pick up to the right idle speed

Reject a car if you have any concerns. Cars are too often an emotional rather than a rational choice. If in doubt, sleep on it and make a decision in the morning

Tim said: “Getting a new car, whether it’s brand new or new to you, is an exciting time. It’s also an expensive time, so the last thing you want is to pick a bad model. Do your preparation before you go so you know what you’re looking for. If you’re not confident, take a friend, get it checked at a garage, or ultimately walk away.”